Structural parameters of interdigitated back contact (IBC) crystalline silicon solar cell are investigated systematically by numerical simulation. The influences of the Si wafer thickness, the area ratio of emitter, gap and back surface field, and the distribution and linewidth of metal contact lines in emitting region on the open-circuit voltage, short-circuit current density, filling factor and conversion efficiency of solar cell are analyzed in detail. Results show that the conversion efficiency of solar cell increases with the increasing of area ratio and the decreasing of metal contact′s linewidth. When the bulk thickness of Si is 220 μm, the area ratio of emitting region, gap and back surface field is 8∶1∶1, the total linewidth of two metal contact lines in emitting region is 10 μm, and an optimum photoelectric conversion efficiency of 24.19% can be achieved for IBC solar cell.